Thumb CMC Arthritis Injections: Corticosteroids, Hyaluronic Acid, and PRP Explained

What injections are given for CMC arthritis?

Injections for carpometacarpal (CMC) joint arthritis primarily aim to reduce pain and inflammation, with common options including corticosteroids, hyaluronic acid (viscosupplementation), and platelet-rich plasma (PRP), each offering distinct mechanisms of action and benefits.

Understanding CMC Arthritis

The carpometacarpal (CMC) joint, also known as the basal joint of the thumb, is located at the base of the thumb, connecting the first metacarpal bone to the trapezium bone in the wrist. This saddle-shaped joint allows for a wide range of motion, crucial for pinching, gripping, and fine motor tasks. Due to its frequent use and unique biomechanics, the CMC joint is highly susceptible to degenerative changes, leading to osteoarthritis.

CMC arthritis symptoms typically include:

• Pain at the base of the thumb, especially with pinch or grip activities.
• Stiffness, particularly in the morning or after periods of inactivity.
• Swelling and tenderness over the joint.
• Aching pain that may radiate into the wrist or forearm.
• Decreased range of motion and strength, making everyday tasks difficult.
• A grinding sensation or sound (crepitus) with movement.

The Role of Injections in CMC Arthritis Management

Injections are a common non-surgical intervention for CMC arthritis, often considered when conservative treatments like rest, splinting, oral anti-inflammatory medications, and physical therapy have not provided adequate relief. The primary goals of injection therapy are:

• Pain Reduction: Alleviating discomfort to improve daily function.
• Inflammation Control: Reducing swelling and inflammation within the joint.
• Delaying Surgery: Providing symptom relief that may postpone the need for surgical intervention.

It's important to understand that injections are generally a symptomatic treatment, meaning they address the symptoms rather than curing the underlying degenerative process of arthritis.

Common Injections for CMC Arthritis

Several types of injections are utilized for CMC arthritis, each with a different mechanism and potential benefits.

Corticosteroid Injections (Steroid Shots)

Mechanism of Action: Corticosteroids are potent anti-inflammatory medications. When injected directly into the CMC joint, they reduce inflammation, which is a major contributor to pain and swelling in arthritic joints. The corticosteroid is often mixed with a local anesthetic to provide immediate, short-term pain relief.

Benefits:

• Rapid onset of pain relief, often within a few days.
• Significant reduction in inflammation.
• Improved thumb function and grip strength.

Considerations:

• Duration of Effect: Pain relief is temporary, typically lasting from a few weeks to several months.
• Repeat Injections: While effective, repeated corticosteroid injections into the same joint are generally limited due to potential side effects. Frequent injections can potentially weaken tendons, thin cartilage, or lead to other local tissue damage. Most clinicians recommend no more than 2-3 injections per year into a single joint.
• Steroid Flare: Some individuals may experience a temporary increase in pain for 24-48 hours after the injection before improvement.

Hyaluronic Acid Injections (Viscosupplementation)

Mechanism of Action: Hyaluronic acid (HA) is a natural component of synovial fluid, the lubricating fluid found in healthy joints. In arthritic joints, the quality and quantity of HA are diminished. Injecting synthetic HA aims to supplement the joint fluid, improving its viscosity and elasticity. This acts as a "joint lubricant" and shock absorber, potentially reducing friction and pain.

Benefits:

• Can provide longer-lasting pain relief compared to corticosteroids for some individuals.
• May improve joint mobility and function.
• Considered to have fewer systemic side effects than corticosteroids.

Considerations:

• Evidence for CMC: While widely used for knee osteoarthritis, the evidence for its effectiveness in CMC arthritis is less robust and more varied. Some studies show benefit, while others do not.
• Onset of Action: Relief may take longer to manifest compared to corticosteroids, often several weeks after the injection series.
• Cost: Generally more expensive than corticosteroid injections.

Platelet-Rich Plasma (PRP) Injections

Mechanism of Action: PRP therapy involves drawing a small amount of the patient's own blood, processing it to concentrate the platelets, and then injecting this platelet-rich plasma back into the injured or arthritic joint. Platelets contain numerous growth factors and signaling proteins that are crucial for tissue healing and regeneration. The theory is that these growth factors can stimulate cellular repair, reduce inflammation, and potentially slow down cartilage degeneration.

Benefits:

• Utilizes the body's natural healing mechanisms (autologous).
• Potential for longer-term pain relief and functional improvement.
• May have regenerative properties, though more research is needed to confirm this for arthritis.

Considerations:

• Emerging Therapy: While gaining popularity, PRP for CMC arthritis is still considered an evolving treatment. The evidence base is growing but not as extensive or universally accepted as for corticosteroids.
• Cost: PRP injections are typically not covered by insurance and can be expensive.
• Preparation Variability: The concentration of platelets and growth factors can vary significantly based on the processing system used, which may influence outcomes.
• Autologous Conditioned Plasma (ACP): A related therapy that also uses the patient's own blood, focusing on anti-inflammatory proteins and growth factors. It's often grouped with PRP or considered a specific form of it.

The Injection Procedure and Post-Injection Care

The injection procedure for CMC arthritis is typically performed in an outpatient setting.

Procedure Steps:

1. Preparation: The skin over the thumb base is cleaned thoroughly with an antiseptic solution.
2. Localization: For precise placement, the clinician may use anatomical landmarks or, increasingly, ultrasound guidance to visualize the joint and needle in real-time.
3. Injection: The chosen medication is injected directly into the joint space.
4. Bandage: A small bandage is applied to the injection site.

Post-Injection Care:

• Activity Restriction: Patients are usually advised to avoid strenuous thumb activities, heavy lifting, and repetitive gripping for 24-48 hours after the injection.
• Ice/Heat: Applying ice to the injection site can help reduce any post-injection soreness.
• Monitoring: Watch for any signs of infection (e.g., increased redness, swelling, severe pain, fever) and contact your doctor if they occur.

Potential Risks and Side Effects

While generally safe, injections carry some potential risks:

• Pain and Bruising: Temporary soreness, swelling, or bruising at the injection site.
• Infection: Although rare with sterile technique, there is a small risk of joint infection.
• Allergic Reaction: A rare possibility to the injected medication or local anesthetic.
• Nerve or Tendon Damage: Extremely rare, especially with ultrasound guidance.
• Corticosteroid-Specific Risks:
  • Steroid Flare: A temporary increase in pain.
  • Skin Atrophy/Discoloration: Thinning or lightening of the skin at the injection site.
  • Elevated Blood Sugar: Temporary increase in blood glucose levels in diabetic patients.
• PRP/HA-Specific Risks: Generally limited to local pain or swelling, as these involve natural substances or the body's own blood.

When Injections Are Not Enough: Other Management Options

If injections provide only minimal or short-lived relief, or if the arthritis progresses significantly, other management strategies may be considered:

• Continued Conservative Management: This includes bracing/splinting, occupational therapy for joint protection techniques, and ongoing physical therapy to maintain strength and mobility in surrounding areas.
• Oral Medications: Continued use of NSAIDs or other pain relievers.
• Surgical Intervention: For severe cases, various surgical procedures can provide long-term relief. These may include:
  • Trapeziectomy: Removal of the trapezium bone.
  • Ligament Reconstruction and Tendon Interposition (LRTI): Removing the trapezium and filling the space with a rolled-up tendon.
  • Arthrodesis (Fusion): Fusing the joint to eliminate pain, though it sacrifices motion.
  • Arthroplasty (Joint Replacement): Replacing the joint with an artificial implant.

Conclusion: A Personalized Approach

Managing CMC arthritis often requires a multi-faceted approach, and injections play a valuable role in alleviating symptoms for many individuals. The choice of injection type depends on various factors, including the severity of arthritis, patient preferences, previous treatment responses, and the clinician's expertise. It is crucial to have an open discussion with a hand specialist, orthopedic surgeon, or rheumatologist to determine the most appropriate injection and overall treatment plan for your specific condition. Injections, when used judiciously and as part of a comprehensive management strategy, can significantly improve quality of life and function for those suffering from CMC arthritis.